1. Field of the Invention
The field of the invention is electronic motor drives for controlling speed and torque of an AC motor.
2. Description of the Background Art
Motor drives typically employ a velocity regulator in which proportional and integral functions are applied to an error signal and the results are summed to form an output. The error signal is an algebraic sum of inputs of position error or velocity reference and velocity feedback, and the resultant output is a torque command.
In one particular application of motor drives to motors on a paper processing line, a long web of material is wound over rollers at a certain tension. During tuning of the system for response to line transients, the change in position of a swing bar on a rolling member, known as a "dancer", may be considered to simulate a typical disturbance.
The general technical problem is the maintenance of overall line speed of the web feeding operation while smoothly damping out tension disturbances applied to the web.
The difficulty in applying prior approaches has been the coupling or interdependence of position and velocity feedback loops, which makes tuning of the control circuit very iterative and difficult.
Feedforward has been used for a variety of control purposes, but has traditionally been a factor that is added to regulator output signals.